Micromechanical components, such as acceleration or yaw-rate sensors used in the automotive industry, usually have a movable mass which is deflectably suspended on a substrate via spring structures. The movable mass is also referred to as a microstructure or MEMS (microelectromechanical system) structure.
In a conventional method for manufacturing a micromechanical component, a layer system is formed on a substrate which includes a relatively thin buried polysilicon layer, a sacrificial layer, and another relatively thick polysilicon layer above the buried polysilicon layer. The buried polysilicon layer is used as a printed conductor plane, and the other polysilicon layer is used as a functional layer. To expose the polysilicon functional layer and thus make available a movable mass, a trench etching process and a sacrificial layer etching process are carried out.
Another method for manufacturing a micromechanical component in which a layer system is formed on a substrate, which includes three polysilicon layers situated one on top of the other and sacrificial layers situated in-between, is described in German Patent Application No. DE 10 2007 060 878 A1. Here, it is provided to expose the upper polysilicon layer and the middle polysilicon layer, thus resulting in two functional layers being situated one on top of the other. The middle functional layer may also be used as a printed conductor plane or as an additional mechanically self-supporting or deflectable layer. It is possible to manufacture mechanically self-supporting elements from the individual functional layers or from any combination of the two functional layers.
The above-named manufacturing processes cannot be used to form micromechanical elements which are both electrically isolated from one another and mechanically coupled to one another. Such an electrically insulating coupling would, however, be advantageous for various micromechanical sensors. Alternative techniques for manufacturing self-supporting and mechanically coupled as well as electrically isolated structures are associated with relatively great expenditures.